Hydraulic press



sept.. 5, 1944. R, CORNELlUs l 2,357,632

HYDRAULIC PRESS r l Filed Aug. 11, 1941 5 shets-sheet 1 RcRard l Crnelius Sept. 5, 1944. v R. T. CORNELIUS'. 2,357,632

HYDRAULId'PREss Filed Aug. 11, 1941 5 sheets-sheet 2 K-'Liardv T. Cornelius Sept. 5, 1944. R. T. CORNELIUS 'HYDRAULIC PRESS Filed Aug. 11', 1941 5 Sheets-Sheet v3 Sept. 5, 1944. R T- CORNELlUs 2,357,632

HYDRAULI C PRE S S Rha1fd T. Cornelius Pateated Sept. V, 1944 UNITED s'rivrizsg PATENT `OFFICE msinsss Richard T. Cornelius, Minneapolis, Minn. Application August 11, 1941, semi No. r406,342

(ci. so-54.5)

14 Claims.

My invention relates to hydraulic presses and has for an object/ to provide a hydraulic press capable of exerting an extremely high pressure.

Another object of the `invention resides in providing a hydraulic press .utilizing a single rotary pump for procuring the liquid under pressure employed tooperate the press.

An object of the invention resides in providing a hydraulic press having a press cylinder and a piston therein for procuring relative movement between the press platen and bed and in providing means for exerting different degrees ,of pressure in said press cylinder to procure rapid initial travel and slower iinal travel with greater pressure.

Another object of the invention resides in providing a pump cylinder adapted to communicate with said press cylinder and having a pump piston therein and in further providing a highv pressure cylinder having a high pressure piston therein connected with the pump piston andop- -erated thereby. l*

A feature of 4the invention resides'in providing a reservoir having a gas and a liquid therein under pressure Icommunicating with the pump `cylinder on one :side fof -said pump piston for :causing return movement of the high pressure piston.

An object of 'the invention resides in maintain- A-ing said reservoir in communication with the pump cylinder at all times.

.Another obgiect of the invention resides in providing a ,passageway between said portion of the ypump cylinder to which the reservoir is con- .nected and the press cylinder whereby the liquid under pressure in said reservoir causes relative movement between platen and bed toward each other.

An object of the invention resides in providing valve means in said passageway and in providing means controlled by movement -of the pump -cylinder for actuating said valve means.

v cylinder.

An object of the invention resides in providing means operated by the motor-driven pump for moving said press piston in said press cylinder to procure relative movement between the platen and bed away from each other.

`A feature of the invention resides in arranging the passageway between the press cylinder and the pump cylinder through the high pressure' piston and in providing a valve at the end oi the high pressure piston for closing said pas sageway. 1

A feature of the invention resides in providing a plunger fixed relative to the pump cylinder- -and passing through the pump piston. said plunger operating to engage the valve and open the same upon the pump piston reaching one of its extreme positions.

Other objects of the invention reside in the f novel combination and arrangement of parts and hydraulic press illustrating an embodiment of my invention.

Fig. 2 is a plan view of the invention.

Fig. 3 is a fragmentary plan sectional view taken on line 3-3 of Fig. 1.

Fig. 4 is a diagrammatic view of the invention showing the parts arranged in ycertain positions.

Fig. 5 is a view similar to Fig. '4., yshowing the parts in altered positions.

Fig. 6 'is a view similar to Figs. 4 and 5 .showing the parts in still different positions.

My invention comprises a frame work A on which is supported a hydraulic press B embodying the principal features of the invention, a tank C and an electric motor D driving a pump E. These various parts will now be described in detail.

- The tank C is constructed of heavy sheet material having side walls III and Il, end walls I2 and I3, a top I4 and a bottom I5. These various parts are secured together by welding ai the corners to provide a rigid and substantial construction. At one end of the tank is provvided a filler cap I6 which lis disposed near the corner between the walls II and I2. Near the wall Il is arranged an outlet pipe I'I which ex tends down into the tank and which is provided with a strainer (not shown) by means of which the liquid used in the system is cleared of impurities before entering the press proper. At the corner between the walls I0 and I2 is provided a return pipe I8 by means of which the oll discharged from the press is returned to the tank C.

tally extending channel-shaped frame members 2|, 22 and 23 which are welded together at the corners. The ends of the frame members 2| and 22 are welded to the wall IU of the tank C. A fourth horizontally extending frame member 24 is also welded to the wall I0 of tanl: C and lies parallel with the frame member 22. The framework A is supported on four legs 25 which are welded to the frame members 2|, 22 and 23 and to the bottom of the tank C at the outermost corners thereof.

The hydraulic press proper consists of a planiform base 26, best shown in Fig.A 3, which rests upon the uppermost flanges of the frame members 22 and 24 and which is secured thereto by means of bolts 21. 'I'he base 26 is provided with four vertically extending guides 20 in which are slidably mounted four posts 28, the posts 28 extending throughout the length of the machine. These posts are attached at their lower ends to a cross head 29 and at their upper ends to the platen 3| of the press. This is accomplished by reducing the ends of the post 28, as indicated at 32 to form shoulders 33 which butt against said cross head and platen, said ends being threaded as des-'gnated at 34 to receive nuts 35 whichv clamp the parts and hold the said cross head and platen against the shoulders 33. This assembled structure forms the ram of thepress which is indicated by the reference numeral 2|).

Mounted on the base 26 is a cylinder 36 which is constructed with a bore 31 at one end of a certain diameter and with a bore 38 at its other end of a somewhat reduced diameter. Said cylinder is received within a recess 39 in the base 26. A cylinder head 4| rests upon the upper end of the cylinder 31 and is constructed with a groove 42 in which the upper edge of the wall of the said cylinder is received. This cylinder head y also forms the base for another cylinder 43 which supermposes the cylinder 31 and is concentrically arranged relative thereto. The cylinder 43 is received within a groove 44 formed in the upper surface of the cylinder head 4|. The upper end of the cylinder 43 is closed by means of the bed of the press which is indicated by the reference numeral 45. Extending between the bed 45 and the base 26 are a number of tie rods 41 which tie the entire structure together and maintain the cylinders and the parts connected therewith in proper relation. These rods are threaded at their upper ends to screw into the bed 45 and are threaded at their lower ends to receive nuts 5| which draw the parts securely together. inder for procuring relative movement between the bed 45 and platen 3|, while the cylinder 43 constitutes a pump cylinder for increasing the pressure within the cylinder 31 in a manner to be presently described in detail.

The bed 45 of the press is provided with four guides 46 similar to the guides 21 which receive the posts 28. These guides together with the guides 2U support the ram 20 of the press for movement. Both the bed 45 and the platen 3| are formed with tapped holes 9| into which suitable bolts may be screwed to attach the die members to the same.

Slidably mounted within the cylinder 36 is a piston 52 provided with cup leathers 53 which form in conjunction with the bore 31 of cylinder 36. a fluid-tight connection. This piston is constructed with a stem 54 which screws into a stout piston rod 55 which lts closely within the bore 38 of cylinder 36. A tight joint is affected The cylinder 31 forms the press cylbetween the cylinder 36 and the piston rod 55 by means of a stufng box 56. The piston rod 55 is provided with a stem 51 which passes through the cross head 29 and which receives a nut 58 bymeans of which the said piston rod is securely attached to the cross head 29. By means of this construction, a chamber 6| within the cylinder 36 is provided which is disposed upon the upper side of the piston 52. When fluid under pressure is directed into this chamber, the piston 52 travels downwardly, procuring relative movement between the platen 3| and the bed 45 toward one another. At th same time a chamber 62 is formed on the under side of the piston 52 and encircling the piston rod 55, which chamber is of considerably smaller dimensions than the chamber 6|. When uid under pressure is directed into this chamber, the piston 52 rises and relative movement Abetween the platen 3| and the bed 45 is had in a direction away from one another. For the sake of convenience, I have referred to the chamber 6| as the power chamber of the press cylinder and the chamber 62 of said cylinder as the return chamber of the cylinder.

Within the cylinder 43 is slidably mounted a pump piston 63. This piston is constructed with cup leathers 64 by means of which a tight joint is had between the piston andthe bore of said cylinder. Attached to the piston 63 is a high pressure piston 65 which passes through the cylinder head 4|. A stuffing-box 66' mounted on the cylinder head 4| and encirclingthe piston 65 forms a fluid-tight connection between said piston and the cylinder head 4|. -The bore of said stuffing-box through which the piston 65 operates, constitutes a high pressure cylinder which I have indicated by the reference numeral 61 and The pisin which the said piston 65 operates. ton 63 divides the interior of the cylinder 43 into a chamber 14 which is disposed above said piston and which I have termed the power chamber of the said cylinder. In addition, the said piston forms an annular chamber 15 within the cylinder 43 encircling the piston 65 and disposed below the piston 65. This chamber I have termed the return chamber of the pump cylinder.

In the bottom of the piston 65 is provided a poppet valve 68 which is slidably mounted in a guide 69 formed in the piston 65. This piston has a valve opening 1| adapted to be closed by the valve 68 which communicates with a passageway 12 in said piston, said passageway extending longitudinally of the piston. In proximity to the piston 63,. cross passageways 13 are provided, which bring the passageway 12 into communication with the chamber 15 on the under side of the piston 63. The valve 68 is urged into closing position by means of a spring 16 which encircles the stem of the said valve and is seated against a collar 11 attached to the end of the same. 'I'he valve 68 is adapted to be unseated by means of a plunger 18 which is screwed into the bed 45 upon the under side thereof. This plunger extends through the piston 63 and into the passageway 12. A stuflng-box 19, attached to the piston 63, forms a huid-tight connection between the said piston and plunger. When the piston 63 reaches its uppermost position, the end of the plunger 18 engages the valve" stem 10 of the valve68 and unseats the said valve, bringing the chamber 6| into communication with the chamber 15.

For the purpose of illustrating the application of my invention, a mold 8| is shown in Fig. 1.

'rms mcia consists ci c. die bicck a2, having c cavity a: in it in which is formed c. cup-shaped member 34. A similar die-block 85 is formed with complemental projection 88 which, when in-y serted into the cavity83, forms the molded product. The die block 82 rests upon a heater 81 which, in turn, rests upon parallel bars 88, un-

derlying the upper surface of the bed 45. The die block 82 has bolts 89 extending through the same, which are screwed into the tapped holes 9| therein. tached to the platen 3|. When the mold cavity is illled with plastic material and the platen and bed moved toward each other, the material in the mold cavity is compressed and heated to form the ultimate product.

A pipe 92, screwed into the bed 45 is connected with a passageway 93, which communicates with the chamber 14 of cylinder 43. A pipe 90, threaded into the cylinder head 4| is connected to a passageway 94 which communicates with the chamber 15 of cylinder 43. A pipe 95 threaded into the cylinder 36at the locality ofthe bore 38 vcommunicates with the chamber 82 of cylinder 36 through a passageway 96. The pipe 90 is connected to a reservoir 91 by means of another pipe |02 which pipe extends down into the said reservoir in close proximity to the bottom thereof. The reservoir 91 is mounted on the framework A. Issuing from the side of the reservoir are lugs 98 which are bolted to the flanges of the frame member 2| by means of bolts 99. A sight glass I| is secured to the reservoir 91. It will be noted that the chamber 15 is at all times in communication with the reservoir 91. The servoir 91 is illled partly with oil or Whatever liquid is to be used in the operation of the press. This oil is maintained under pressure by directing compressed air into the said reservoir at the uipper end thereof through a pipe |03 which is connectedv to the said reservoir and to a source of compressed air. A valve |04 in said pipe shuts oifi the air when the pressure in the reservoir 91 la suilicient.

The motor D and the pump E may be of standard construction. 'I'he motor D is provided lwith a base |05 which 'is attached to the top I4 of The die block 85 is similarly at lasuman wardly through the device and has attached to it an operating lever |23 by means of which the piston assembly |-I0 may be4 reciprocated within the bore II1. Formed in the valve ||6 are ports |24, |25; |28, |21, |28 and |29. 'I'he pipe II5 leading from the pump E has two branches |3| and |32 which are connected to the ports |21 and |28. The return pipe I8 leading they tank'C is connected-to two branch pipes |33 and |34 which, in turn, are connected to the ports |28 and |29. The port |25 is connected by means of a pipe |38 with a relief valve |38 which in turn is connectedto the pipe 95. The other port |24 of the valve 6 is connected by means of a pipe |38 with a relief valve |39. 'Ihis relief valve is connected to the pipe 92. Both the relief valves |38 and |39 are provided with by-pass pipes |4| and |42 which are connected to the return pipe I8. ,The two relief valves |38 and |39 are operated under considerable pressure and have connected to them control valves |43 and |45. The valve |45 has a pipe |48 connected to the cylinder of valve |39 and another pipe |41 connected to the return pipe I8. Likewise, the valve|43 has a pipe |48 connected to the cylinder of the valve |38 and a pipe |49 connected to the return pipe I 8. By adjusting-the control valves |43 and |45 the pressure within the valves |36 and |39 may be regulated. As previously brought out, the reservoir 91 is filled with liquid up to the level indicated at |5| and with a gas indicated at |52 above the liquid. For I the purpose of the invention air under pressure may be used as the gas which is delivered into said reservoir at the top thereof through the Pipe |03 previously referred to. YThe fpipe 93 which is connected to the reservoir 91 extends the tank C by means of bolts |06. This motor `thereof is in lalignment with shaft |01 of motor down toward the bottom of said reservoir so that the pressure of the gas |52 will raise the liquid in said pipe and force it into the piston chamber 15.

'Ihe operation of the invention is as follows:

-Assume that the parts are arranged as shown in Fig. 4. The pump E delivers liquid under pressure to the valve I I6, which liquid passes through the port |28 and port |25 into the pipe |35. The liquid then passes through the valve |38 and pipe |95 into the cylinder chamber 62. This urges the piston 52 upwardly and separates the platen 3| and bed 45.- After the platen' 3| reaches its ultimate position the valve |36 opens and the surplus liquid passes through pipe I4| into the return pipe I8 and back to tank C. At

D. The inlet to the pump E is connected by means of a pipe ||4 with the outlet pipe I1 oi' tank' C, so that the liquid within the said tank is delivered to the pump and discharged therefrom throughA the discharge outlet of said pump. Connected tothe discharge outlet of the pump E is avpipe I I5 which is connected in the system as will be presently described in detail.

In Fig. 4- I have shown in diagrammatic form the piping connected to the various parts of my improved hydraulic press. operation of the press a manually operable controlled valve II8 is employed which has a bore I I1 extending throughout the length thereof and closed at its ends. Slidably mounted in the bore ||1 is a piston assembly |I0 having three pistons |I8, ||9 and I 2| which are mounted on a single plunger 22. Plunger |22 extends out- For controlling the i due to the fact that the port |24 is in communi cation with port |28 and the port |25 is in communication with the port |28. These cylinder chambers are thus not under pressure. The gas |52 in reservoir 91 being under pressure forces the liquid through the pipe 90, as indicated in Fig. 5, and into the cylinder chamber 15. The liquid passes through the passageways 13 and 12 and 'past the valve 88 into the cylinder chamber 8|. Cylinder chamber 82 being connected to the return pipe I8, as previously described, the

piston 52 lowers and the platen 3| is caused to move toward the bed 45 and to bring the two parts of the mold 8| together. If a pressure of 100 lbs. per square inch is maintained in the reservoir 91 surfdcient movement of the platen -is procured to bring the parts of the mold into almost closing position. Thus the platen moves quickly into a position in proximity to its final position.

Movement of the platen into final position is procured by moving the lever |23 to its position shown in Fig. 6. In Fig. 5 the piston 52 has been shown as partly lowered. When the lever |23 is moved to the position shown in Fig. 6 port |21 is connected with port |24 and port |26 is closed. This causes the pump E to force the liquid through pipe ||5, pipe |38, through valve |39 and through pipe 92 into cylinder chamber 14. The pump E is designed to exert a pressure of from 500 to 1000 lbs. per square inch. This causes the piston -63 to descend. Inasmuch as piston 65 is connected to the piston -63, the same travel together. Upon initial movement of the piston 63 spring 16 closes valve 68 and the flow of iiuid through the passageways 13 and 12 terminates. The forcing of piston 65 into the cylinder chamber 6| increases the pressure therein in proportion to the inverse ratio of the dlameters of the pistons 65 and 63. If the ratios of these pistons are 5 to 1 a pressure of 4500 lbs. per square inch can be had in the cylinder chamber 6| which causes ilnal movement of the platen 3| to close the mold 8|. During movement of the piston 63 the cylinder chamber 62 is still connected to the return pipe I8 since ports |29 and |25 are in communication. The mold is then allowed to remain the necessary time in closed position to permit the heater 81= reservoir 91. This establishes the original presy sure in the said reservoir.

Upon lapse of required time for the curing of the molded product in mold 8| lever |23 is returned to its position shown in Fig. 4. This connects port |24 with port |26 thus connecting cylinder `chamber 14 with the return pipe I8. At the same time port |28 is connectedto port |25 so that the pump E delivers fluid under pressure I to cylinder chamber 62. .This causes the piston 52 to rise and the piston l63 aided by the pressure against the valve 68 forming a part of piston and the pressure in cylinder chamber 15 occasioned by the pressure in reservoir 91 causes mum amount of power to operate. The opening of the press and the initial closing vof the press is accomplished very rapidly so that loss of time is eliminated. Only when the press is moved to nal position is the speed of the movement reduced. The press may be used for molding plastic materials and also for heavy punch press work where great pressure and rigidity is required. With my improved press no valves are required to be manipulated while the pressure is at a maximum thus making it possible to use simple valves and simple operating mechanisms therefor,

Changes in the specific form of my invention, as herein disclosed, may be made within the scope of what is claimed without departing from the spirit of my invention.

Having described my invention, what I claim as new and desire to protect by Letters Patent is:

l. In an actuating mechanism for a press having a bed and a platen guided for relative movement, a means forming an expansible press chamber including a press, piston lacting to procure relative movement between said bed and platen and a high pressure piston, a pump cylinder, a

' piston therein for operating said high pressure piston, a reservoir containing a liquid and a gas under pressure, means for connecting said pump cylinder to said reservoir to procure return movement of said high pressure piston, means for connecting said press chamber to said reservoir to procure relative movement between said bed and platen toward one another, means for subjecting said pump piston to a fluid under pressure to procure pumping action of the high pressure piston and further movement between said bed and platen, and means for procuring movement of the bed and platen away from each other.

2 In a hydraulic press including a bed and a platen movable relative to one another, means forming an expansible press chamber and including a high pressure piston and a press piston, said press piston when fluid under pressure is directed into the press chamber causing relative movement of the bed and platen toward one another, means forming an expansible pump chamber and an expansible return chamber, said means including a pump piston, said high pressure pisi ton being operated by said pump piston, said The advantages of my invention are manifest.

The device operates with but a single rotary pump. This pump may be a gear pump which is relatively inexpensive. vIn a gear pump pressures from 500 to 1000 lbs. per square inch are easily attained. Thus with the proper power advantage of the auxiliary pump cylinder and high pressure cylinder, pressure up to 4500 lbs. per square inch can be procured where a pressure of 100 lbs. per square inch is maintained in the pressure reservoir. My improved hydraulic press operates extremely efficiently requiring but a minipump piston when a iiuid under pressure is directed into said pump chamber causing pumping action of said high pressure piston and when directed into the return chamber causing return movement of the high pressure piston, a reservoir containing a liquid and gas under pressure, a conduit communicating with the liquid in said res- `ervoir and connected to said return chamber,

means forming a valve-controlled passageway connecting said conduit and said press chamber and means for conducting iiuid under pressure into the pump chamber to compress the fluids in said reservoir and to operate said high pressure piston.

3. In a hydraulic press including a bed and a' is directed into the press chamber causing relative movement of the bed and platen toward one another, means forming an expansible pump chamber and an expansible return chamber, said means including apump piston, said high pressure piston being operated by said pump piston, said pump piston when a iiuid under pressure is directed into said pump chamber causing pumpaszesa 5 ing action uf said high pressure piston and when directed intf .thefreturn chamber causing return movementpthehigh pressure piston, said press piston Vbg'eing""miivable independently-` of the high pressure piston during operative movement of said press piston, a reservoir containing a liquid and gas under'pressure, a conduit communicating with the liquid in said reservoir and connected to said return chamber, and means forming a valve-controlled passageway between said return chamber and press chamber for conducting liquid from said return chamber and into said press chamber.

4. In a hydraulic press including a bed and a platen movable relative to one another, means forming an expansible press chamber and including a high pressure piston and a press piston, said press piston when uid underpressure is d.- rected into the press chamber causing relative movement o'f the bed and platen 'toward one 'another, means forming an expansible pump chamber and an expansible return chamber, said means including a pump piston, said high pressure piston operated by said pump piston, said pump piston when a fluid under pressure is directed into said pump chamber causing pumping action of said high pressure piston and when directed into the return chamberv causing return movement of the high pressure piston, `a reservoir containing a liquid and gas under pressure, a conduit communicating with the liquid in said reservoir and connected to said return chamber, said high pressure piston having a longitudinally extending passageway therein communicating at one end with thereturn chamber and extending through the opposite end of the high pressure piston and comf municating with the press chamber at such end,

being operated by said pump piston, said pump piston when a fluid under pressure is directed iinto said `pump chamber causing pumping action of said highpressure piston and whenfdirected into the return chamber causing return movement of the high pressure piston, a reservoir containingla liquid and gas under pressure, a conduit communicating with the liquid in said reservoir and connected torsaid return chamber, said return chamber being at all times connected to said reservoir and means forming a valve-controlled passageway between said return chamber and press chamber for conducting liquid from said return chamber and into saidv press chamber.

5. In a hydraulic press including a bed and when affluid,l under pressure is directed into said pump chamber causing ypumping action of said high pressur'e` piston` and when directed into the return chamber causing return movement of the high pressure piston, said press piston being movable independently of the high pressurepiston during operative movement of said press piston,

a' reservoir containing a liquid and gas under pressure, a conduit communicating with the liquid in said vreservoir and connected tosaid return 1 chamber, said high pressure piston having a passageway therein communicating with said press chamber and saidreturn chamber, and conductingliquid from said return chamber to said press chambena valve in said-passageway. and means operated by said pump piston for opening .said va ve.

a valve seatformed on the high pressure piston at.

the last named end thereof and a valve engaging said seat and held in engagement therewith through the pressure in said press chamber.

7. I n a hydraulic press including a bed'and a platen movable relative to one another, means forming an expansible press chamber and including a high pressure piston and a press piston, said press pistonwhen uid under pressure is directed into the press chamber causing relative- 1 movement'of the bed and platen toward one another, means forming an expansible `pump chamber and an expansible return chambensaid means including a pump piston, said high pressure piston being operated by said pump piston, said pump piston when a fluid under pressure is directed into said pump chamber causing pumping action of said high pressure piston and when directed Ainto the returnchamber causing return ,movement of the high pressure piston, a reservoir containing a liquid and gas under pressure, a conduit communicating .withthe liquid in said reservoir and connected to said return chamber, said high pressure piston having a longitudinally extending passageway therein communicating 'at one end with the return chamber and extending through theopposite end of the high pressure piston and communicating with the press chamber at such end, a valve seat formed on the high pressure piston at ythe last named end thereof and a valve engagv ing said seat and held in engagement therewith Y through the pressure in said press chamber, and means for unseating said valve and operated by said pump piston.

8. In a hydraulic press including a bed and a platen movable relative to one another, means forming an 'expansible press chamber and including a high pressure piston and a press piston, said press piston .when iiuid under lpressure is directed into the press-chamber causing relative movement of the bed and platen toward one another, means forming an expansible pump chamber and an expansible return chamber, said means including a pump piston, said high pressure piston being operated by said pump piston, said pump piston when a fluid under pressure is directed into said pump chamber causing pumping action of said high pressure piston and when. directed into the return chamber causing return movementof 6. In a hydraulic press including a bed and expansible return chamber, saidmeans including .a` pump piston, said highJpressure pistonrbeing the high pressure piston, said press piston being movable independently of the high pressure piston during'operativemovement of said press piston, and means` forming avalve controlled passageway between said return chamber and press chamber for conductingfluid from said return 'chamber and into said presschamber;A

9. In a hydraulic press including a bedI and a platen movablerelativeto one another; means forming an expansible press chamber and including a high pressure piston and a press piston, said press piston when fluid underpressureis di- 6 i Aarrivasse rected into the press chamber causing Irelative movement or the bed and platen toward one another, means forming an expansible pump chamber and an expansible return chamber, said means including a pump piston, said high pressure piston being operated by said pump piston, said pump piston when a iluid under pressure is directed into said pump chamber causing pumping action of said high pressure piston and when directed intothe return chamber causing return movement of the high pressure piston, said high pressure piston having a passageway therein communicating with said press chamber and said return chamber, during operative movement of said press piston, and conducting liquid from said return chamber to said press chamber, a valve in said passageway and means operated by said pump piston for opening said valve.

10. In a ,hydraulic vpress including a bed and a platen movable relative to one another, means forming an expansible press chamber and includinga high pressure piston and a press piston, said press piston when uid under pressure is directed into the press chamber causing relative movement o! the bed and platen toward one another, means forming an expansible pump chamber and an expansible return chamber, said means including a pump piston, said high pressure piston being operated by said pump piston, said pump piston when a fluid under pressure is directed into said pump chamber causing pumping action of said yhigh pressure piston and when directed into the return chamber causing return movement of the high pressure piston, said high pressure piston having a longitudinally extending passageway therein communicating at one end with the return chamber and extending through the opposite end of the high pressure`piston-and communicating with the press chamber at such end, a valve seat formed on they high pressure piston at the last named end thereof and a. valve engaging said seat and held in engagementltherewith through the pressure in said press chamber.

11. In a hydraulic press including a bed and a platen movable relative to'one another, means forming an expansible chamber and including .a high pressure piston and a press piston, said press piston when iluid under pressure is directed into the press chamber causing relative movementor the bed and platen toward one another, means forming an expansible pump chamber and an expansible return chamber, said means including a pump piston, said high pressure piston being operated by said pump piston, said pump piston when a fluid under pressure is directed into said pump chamber causing pumping action of said high pressure piston and when directed into the return chamber causing return movement of the high pressure piston, said high pressure piston having a longitudinally extending passageway therein communicating at one end with the return chamber and extending through the opposite end of the high pressure piston and communicating with the press chamber at such end, a valve seat formed on the high pressure piston yat the last named end thereof and a valve engaging said seat and held in engagement therewith through the pressure in said press chamber, and means for unseating said `valve and operated by said pump piston.

l2. A control device for a hydraulic press including a bed and Va. ,platen movable relative to one another, means forming an expansible press chamber and including a high pressure piston and a press piston, said press piston when fluid under pressure is directed into the press chamber causing relative movement of the bed-and platen toward one another, means forming an expansible pump chamber and an expansible return chamber, said means including a pump piston, said high pressure piston being operated by said \pump piston, said pump piston when a fluid under pressure is directed into said pump chamber causing pumping action of said high pressure piston and when directed into the return chamber causing return movement of the high pressure piston, said control device including a reservoir containing a liquid and gas under pressure, a conduit connected to said return chamber and communicating with the liquid in said reservoir, means forming a valve-controlled passageway between said return chamber and said press chamber for conducting iluid under pressure from the return chamber to said press chamber duriniir operative movement of the press piston and means for conducting fluid under pressure to said pump chamber.

13. In a hydraulic press including a bed and a platen movable relative to one another, means forming an expansible press chamber and including a high pressure piston and a press piston, said press piston when iluid under pressure ls directed into the press chamber causing relative movement ofthe bed and platen toward one another, means rorming an expansible pump chamber.' and-` an expansible return chamber, said means including a pump piston, said high pressure piston being operated by said pump piston, said pump piston when a fluid under pressure is directed into said pump chamber causing pumping action of said high pressure piston and when directed into the return chamber causing return movement of the high pressure piston, a reservoir containing a liquid and gas under pressure, a conduit communicating with the liquid in said reservoir and connected to said return chamber, said high pressure piston having a longitudinal passageway communicating at one end with said posed within the confines of the return chamber and communicating with said longitudinal pas sageway and said return chamber and conducting liquid from said return chamber to said press chamber and a valve in said passageway.

14. In a hydraulic press including a bed and a platen movable relative to one another, means forming an expansibie press chamber and including a high pressure piston and a press piston. said press piston when iluid under pressure is directed into the press chamber causing relative movement of the bed and platen toward one another, means forming an expansibie pump chamber and an expansible return chamber, said means including a. pump piston, said high pressure piston being operated by said `pump piston. said pump piston when a nuid under pressure is directed into said pump chamber causing pumping action oi' said high pressure piston and when directed into the return chamber causing return movement of the high pressure piston, said high pressure piston having a passageway therein communicating with said press chamber and vsaid return chamber during operative movement of said press piston, andconducting liquid from said return chamber to said press chamber, a valve in said passageway and means movable with said pump piston and engaging a part iixed relative to themeans forming the pump chamber.- said means and part serving to open said valve.

` RICHARD T. CORNELIUS. 

